Although the principles described herein may have application in a variety of contexts, a brief description of the conventional air filter system of the M1 tank provides a general background for understanding the present invention.
As with almost any internal combustion engine, the engine which operates the M1 tank requires large amounts of ambient air for operation. In general, the ambient air is filtered, for removal of particulate matter therein, before it is directed into the gas turbine which powers the M1 tank.
In FIG. 2, a schematic is presented which illustrates the basic operation of the air filter system for the M1 tank, prior to development of the present invention. Referring to FIG. 2, the reference numeral 1 generally indicates the M1 air filter system, for removal of particulate material from the air flow stream which is directed to the engine. Air filter system 1 comprises assembly 2 with inlet (surface) 3 (for ambient air) and outlet 4 (through which clean air is directed to the engine). Assembly 2 defines a two stage air cleaning system. The first or most upstream stage is indicated generally at 7. The second or downstream stage is indicated generally at 8.
The upstream stage 7 comprises a precleaner 10. The precleaner 10 is constructed and arranged for removal of large amounts of particulate material within the ambient air stream, before the air stream is directed into the second stage 8. For the conventional M1 tank air cleaner, precleaner 10 is generally as described in reference to FIGS. 7-10 of U.S. Pat. No. 4,242,115. (The complete disclosure U.S. Pat. No. 4,242,115 is incorporated herein by reference). Such systems are commercially available from Donaldson Company, Inc., Minneapolis, Minn., under the tradename STRATA PANEL. They generally comprise a plurality of centrifugal separators, through which air having particulate material therein is directed. As the air travels through the centrifugal separators, the dust settles in the precleaner 10. The settled dust is removed (scavenged) from precleaner 10 through outlet 11, in a scavenge air stream 12 provided by blower 13. The partially cleaned air exiting the centrifugal separators is directed into the second stage 8, along the path indicated at 15.
Within the second stage cleaner 8, air flow is directed through a particulate filter system, for removal of still more dust and contaminants. The particulates remain in chamber 17 (i.e. in the filters) of the second stage 8, whereas the clean air, after passing through the air filters, is directed through outlet 4 to the engine. A variety of air filter constructions may be utilized within chamber 17. In general, arrangements generally as described in U.S. Pat. Nos. 4,331,459; 4,364,751; and 4,359,330, each of which is incorporated herein by reference, may be, and have been, utilized within chamber 17 in systems similar to, and including, M1 tanks.
During Operation Desert Storm, the M1 tank was operated in an environment (desert) wherein large amounts of fine dust would be picked up in the ambient air and be carried into the air filter'system 1. Even with the precleaner 10 operating at maximum capacity, large amounts of dust were still carried with the air stream 15 directed into chamber 17. While, in general, the air filters positioned within chamber 17 were sufficient for separation of the particulates from the air, the filters and in some instances chamber 17 would rapidly fill with separated dust. As a result, periodically chamber 17 needed to be opened, the filters needed to be removed, and the filters and/or chamber needed to be cleaned of dust or other particulate material. In some instances it was found that the tanks could travel no more than about 10-20 kilometers, before such a cleaning was necessary.
A "plugged" or "clogged" air filter, in the field, for a vehicle such as a tank is no trivial problem. A plugged air filter can render a vehicle immobile. A cleaning of the air filter may require the tank to be stopped, and armor plating to be opened or removed. Indeed, such was found to be the case in Operation Desert Storm.
Also, frequent cleaning of an air filter system in the field presents risks, such as loose dirt, dust or gravel falling into the engine. Thus, it would be preferred to limit the number of times the air cleaner system is opened, in the field.